Circuit breakers are used for interrupting of an electrical circuit by the automatic separation of electrical contacts upon a current overload in the circuit. A conventional circuit breaker relies on a trip element which detects the excessive current and transmits the energy necessary to trip electrical contacts into a spaced apart position. The thermal trip element is sensitive to heat and is based upon an inverse time characteristic. Other types of over current elements are known as the shunted and the shorted turn. The shunted element is heated directly by only a portion of the current that passes through the breaker while the bussing carries the remainder. The shorted turn element is heated by transformer action and is used only in alternating current situations. Magnetic trip elements utilize a coil that is energized upon current increase.
Conventional current trip elements are bi-metal strips reactive to heat allowing the strip to bend. Current passing through the circuit breaker creates heat necessary to trip the element. Ambient temperatures will either add or subtract to the tripping action. Circuit breakers are normally placed in banks of side-by-side units in a distribution panel. An outwardly exposed front face and operating handle is readily accessible and visually observable. The operating handle has two extreme positions, one when the circuit breaker is in a circuit completing position and the other when in a circuit interrupting position. When an overload condition occurs, the circuit breaker is tripped indicating that the load circuit is interrupted simultaneously causing the operating handle to move to an intermediate position.
The detection of tripped circuit breakers lends itself to a problem which one of the inventors has established a well known repertoire of patents. For instance, U.S. Pat. No. 4,056,816 issued to Guim teaching a blown circuit breaker indicator utilizing an LED responsive to an overload position. U.S. Pat. Nos. 4,633,240 and 4,611,201 issued to Guim, et al., teaching a circuit breaker having a battery powered light energized through an auxiliary switch coupled to a breaker. U.S. Pat. No. 5,061,731 issued to Guim, et al., teaches yet another advancement in circuit breaker assemblies.
While Guim exhaustively disclosed devices for detection of tripped circuit breakers, what is found lacking in the art is a means for informing the operator of a latent condition of the circuit breaker, namely, life expectancy. Each time a circuit breaker is tripped due to over current, it causes a cycling which weakens the metal strip. For instance, a circuit breaker overloaded multiple times will result in numerous trip conditions all the result of excessive heating to the strip. In such a situation the circuit breaker will operate according to its designed duty by tripping, thus requiring a person to manually reset the breaker once the overload condition has been corrected. Each time a circuit breaker is tripped, the life of the breaker is shortened as the metal strip is heated and cooled resulting in strain hardening of the metal. Over a period of time this can adversely effect the operation of the circuit breaker to the point of causing premature overload detection or failure to detect an overload condition.
For example, an electrical circuit in a hospital emergency room can be quickly overloaded when a multitude of medical devices are coupled on a single circuit. If the circuit is oversized, no protection is provided to the individual equipment components. For this reason, it is typically mandated that the circuit breaker is routinely replaced so as to prevent such a condition from occurring without having to oversize. However, unless meticulous records are maintained, periodic replacement of all circuit breakers is a costly and inappropriate service procedure. Had the operator been able to account for which circuit breaker had been tripped and how many times that circuit breaker had been tripped, it would be cost effective to simply replace the particular circuit breaker.
Thus, what is needed in the art is a circuit breaker or device that will provide an operator with a numerical count of the number of times a circuit breaker has been triggered. This counting provides an operator with the ability to determine whether or not a particular circuit is continually subjected to an overload situation and a direct indication of how many times the circuit breaker has been tripped so as to determine replacement before failure.